Method for the separation of hydroxy organic acids



Patented May 24, 1949 METHOD FOR THE SEPARATION OF :HY'DROXY ORGANIC ACIDS Willia-mEBarch, Bronx, N. Y., assignor to*Stand- .ard .Brands Incorporated, New York, N. Y., a

corporation of Delaware 'No Drawing. Application June 5,1946,

"SeriaINO. 674,665

.13-Claims. r1

Thelinventionrelates 1130 a method ior the sepaarationiof hydroxy :organic acids. More particularly it (pertains to .a separation of the tartaric acids, and :includes correlated improvements and discoveries whereby (the separation of such acids .one from thelother is facilitated.

An object ,of the invention .is :the provision of a .method in accordance with which hydroxy or ;ganic acids may be separated practically quantiitatively as their substantially pure salts from which !the iiree acids may :be recovered easily 1throughtrcatmentwwith a suitable:acid.

Another :obiect lot the, invention is to provide a method :ior the separation :of vhydroiq or anic acids through .utilization of -a relatively concenl-trated solution of pertain inorganic salts.

'A turther obiectlqfthe invlentioniis the provision (of :a method whereby ,hy-droxy or anic acids may the separated :by treatment with -,a strong :sclution oficalcium-chloride which ,may be ilBllSEd following .the separation.

-A still lfurther ;obiect of the inventionaistmprovide a method for theseparation of lhydroxy organic .acids that may be readily, effectively, and l-economicall fipracticed to a desired .extent'on ;a commercialscale.

A more particular object 015 :the iinventiongis to provide a method :for separating tartaric acids from -:other hydroXy ollganic acids, :especially ior separatingthe tartaricacids from'each other as therdextro :acid from themeso acid, and other zhydroxy aeids,suchlas:saccharioaoid.

.A- specific object of the invention, is to 1 provide .a method. :which effects :.a -,separation of =calcium .dextro, racemic, and;meso-tartrates from oneanother and immpalciumsaccharate by treatment thereof with a .strong -.calcium chloride solution .iollowed rby dilution and formation of basic calcium saltsaof meso-ltartaric andsaccharic acids by :reaction-withpalciumhydroxide.

Other objects qof the invention will .in part be obvious and will ,in part appear hereinafter.

-The linvention accordingly comprises the several stepssand thelrelations Of'OIIEOIVmOYBOf such steps with :respect to each of the {others thereof, whichwill be-exemplified in the method hereinafter disclosed, and the scope of .the invention will be indicated .in .the claims.

In the practice of the invention ,a mixture of salts of .hydroxy Or anic acids, as the tartaric acids saccharic, citric,lactic acids, "and the like for example, .as their calcium salts, or a mixture 10f the acids, is dissolved in a concentrated so1u- "tion,-'i.'-e.-o'f 34-to 47B.which*may be referred 'to'as'a brineof a-highly soluble salt of ametal that "forms -a highly soluble chloride and an insoluble -salt of the 'Ihydroxy 7 organic acid, as :tar-

taric -acid, where'by doublecompounds as .-calcium dextro tartrate-calcium chloride :are;'formed,;and separation of salts so'f the acids effected initially through dilution; whichoccasion hYdIQlYSi'SiOfIIhE least stable double compounds to the normal salts, as calcium dextro it'artrate, .of ithe solution thus :obtained whereupon the :insoluble :normal salt precipitates out. The thus 'separatedinormal salt is removed as "by filtration land the homilydrolyzed or more stabledouble'compoundsiremaining in solution may' be converted .into 'the corresponding insolubletbasicfsaltszby reaction lwithlan alkaline hydroxide, :which basicisaltsyield a cor-- =responding acid mpon treatment thereof :with in stronger acid: desirably an inorgani'c acid such 1 as hydrochloric, sulphuric, phosphoric, and the like. The concentrated:solutiomwithiwhichzthetorganic acid or saltmix-ture isitreatedimayibeofia:chlorlde of a metal that forms :an il'nsoluble :salt with the organic acid :and =-especially ithe chlorides lot :cal-

cium, strontium, magnesium, and zinc. it was discovered, however, thattheyaraallzreadilyssolu- =ble to clear solutions in calcium chloride :brines "of over 3'9"-- B.

'When :these brine :solutions, :containing lthe double compounds, :are diluted :with water, 'the normal.salts,ie.ig. calcium dextroltarltrate, are reprecipitated without r'change. The :amount and .rate of reprecipitation varies widely with the dilution and with theinatureaoi the hydroxy :acid. By proper control of ithe #tiilutioniof ithe "brine .solution, calcium idextro itartrate may (be sepa- :rated from :the other components of the mixed salts linian amount whiohisiguantitative forlall practical 5 purposes. 'In :the same :manner calcium meso-tartrate may be separated, largely, ,although not quantitatively from the balance of the componentspresent.

lcompletesprecipitation from the brine may be obtained i-immediaitely hyitheaddition of a small amount of slaked' lime, 1'0to 30% of the mixed acids or salts thereof, as 'all the acids "present form very insoluble basic salts, anwtheihrinegmay thus be completely cleared of organic'ma'teri'al for recovery and re-use. This recovery is -&QG01'I1-- .plished merely .sby neutralizing the alkalines'spent brine with a little acid,-such as hydrochloric a'cid, sand evaporating to the roriginal Baum.

I have thus found ithat, for example .twoniew soluble double compounds of zcalciumadextro 'tar trate .lHzO and calcium meso-tartrate dHzOand calcium chloride are producediby treatingiWith-a concentrated solution thereof, i. 'e. of a *eoncentration sufiici'ent to form the double compounds. Both of these .are hydrolyzed -by water with pre- :cipitation of the normalsalts. However, 111111181" certain conditions .the calcium mesa-.tartrate- 3 calcium chloride double compound may be stabilized and held in solution. This is illustrated by the following:

When 1 gram of calcium dextro tartrate 41-120 is added to cc. of molten calcium chloride 61-120 (melting point 30) and gently warmed, a bright, clear solution is formed which. is stable to further heating or to indefinite standing at room temperature. Water may be added to the solution up to 1.2 cc., where the solution sets with evolution of heat to a translucent gel. This gel is completely reversible, forming a clearsolution on heating and setting again on cooling. Addition of more water up to 5 cc. produces permanent precipitation and at cc. the calcium dextro-tartrate ll-I is precipitated quantitatively as the normal salt.

One gram of calcium meso-tartrate 31-120 and 5 cc. of molten calcium chloride 6Hz0 forms a solution very readily on gently warming, but on further warming heavy precipitation occurs. This precipitate does not dissolve again on cooling.

A mixture of the two salts in the ratio of gram calcium dextro tartrate and /3 gram calcium meso tartrate and 5 cc. molten calcium chloride 6H2O forms a clear solution. It is stable to heat and the calcium meso-tartrate is no longer precipitated. The solution does not gel as with calcium dextro tartrate alone. When diluted with 10 cc. water, the calcium dextro tartrate is precipitated in about 95% purity and the calcium meso-tartrate-double compound remains in solution.

Somewhat more particularly, the separation of a mixture of calcium salts of the tartaric acids may be brought about by dissolving 10 grams thereof in about 75 cc. of a calcium chloride brine of 39.16 B. followed by dilution to 150- cc. giving a Baum of 24.17, then allowing the diluted solution to remain standing for about three days prior to filtering. The precipitated salt was removed and a, basic precipitation effected in the filtrate by the addition thereto of about 3 grams of calcium hydroxide. The precipitates obtained were analyzed by decomposing the calcium salts with an excess of oxalic acid, removing the oxalic acid excess, half neutralizing with potassium hydroxide, and crystallizing the potassium acid salts from water and methanol. The salts were examined by titration and optical rotation, and the residues which would not crystallize were reconverted into the calcium salts. The following results were obtained:

Calcium Calcium Calcium Dextro Race- Meso Uniden- Tartrate mate Tartrate tified 4H2O 4Hz0 31120 Neutral Precipitaiz'on from Brine by Dilution As KH salt from water 5. 95 0. 29

As KH salt from 50% Methanol 0. l9 0. 14 Residue 0. 18 0. 17

Total by dilution 6. l4 0. 43 0. 13 0. 17

Basic Precipitation from Brine As KH salt from water. 0. 04 v As KH salt from 50% Methanol 0. 32 1. 37 Residue 0. 52 O. 4.7

Total as Basic Salt 0.36 1.89 0. 47

Total Recovered 6. 50 0. 43 2. 02 0. 04

The foregoing tabulation indicates that of the total amount of dextro tartaric and racemic acids 94.9% was present in the precipitate following dilution, and the purity thereof was 95.2%.

As an illustrative embodiment of a manner in which the invention may be practiced, the following description is presented:

Separation of calcium dextro, racemic and mcso-tartrates and calcium sacchamte One thousand pounds of the mixed salts were dissolved by heating and stirring in a 2,500 gallon low pressure steam jacketed kettle by means of a calcium chloride brine containing 7,500 pounds of CaClaGHzO and 300 gallons of water until a clear solution was obtained. The time required for solution was about ten minutes and the volume about 900 gallons. The solution so obtained was immediately diluted without cooling through the addition with stirring of about 900 gallons of water, in other words, in a ratio of solution to water of one to one. After standing for several days crystallization from the diluted brine was substantially complete. The crystalline material was filtered and washed with cold water to free it from calcium chloride. The material was coarsely crystalline, washed easily, weighed about 700 pounds, and was substantially all calcium dextro tartrate. The filtrate from the fore-going filtration consisting of about 2,000 gallons was heated to about C. and about 300 pounds of calcium hydroxide were added with stirring. A finely divided precipitate of basic salts of mesotartaric and sac-charic acid formed and was allowed to settle prior to filtering. The separation of the basic salts frees the brine practically of organic material. The precipitate was washed with hot water, and it amounted to about 600 pounds. It is advisable to collect the wash water separately since it reduces the amount of evaporation in recovering the brine.

The basic salts so obtained were broken up by stirring into 600 gallons of hot water whereupon about gallons of concentrated hydrochloric acid were added and stirring continued until a clear solution resulted. A 20% solution of sodium hydroxide was then added to the hot solution in a thin stream and at a rate such that the locally formed basic salt redissolves and does not accuinulate. Sodium hydroxide is added until about 95% of the acid is neutralized, and this may require about 750 gallons of the 20% solution. Following addition of the sodium hydroxide, the reaction mass was cooled, and allowed to stand whereupon crystallization takes place. It was filtered and washed to free it from soluble chlorides. The material thus obtained amounted to about 200 pounds and was approximately 90% calcium meso-tartrate with 3 molecules of water. The spent brine may be recovered by adding concentrated hydrochloride acid thereto to give the pH value possessed by the original brine, and then evaporated to the original volume of 900 gallons. The brine remains clear and water white, and inasmuch as it contains little or no organic matter, it may be reused with small additions to restore the original strength.

The foregoing procedure eiTects a substantially complete separation of the mixed tartrates, and in carrying out the process, the following factors should be considered. The original brine should be neutral to methyl red, that is a pH value of about 5.1, and it should contain no appreciable amount of other metals particularly the alkali m ss meta-1st The'concentration ofs-thebrinemayzvaryi somewhat irony-39 but it hasrbeem found-that the concentration range should be from about 34? to about 47 B. However, a concentration of. about 39? is preferred. The dilution with an equal amount of water-has been foundfto be the which will yieldalt ofthe" calcium dextro and-raee'm-ici tartratesi It a '-'greater'dil1ttion is. effected, aniamount oi mes'o-tartratwill be precipitated whereas if the-' dilution is o a lesser extent as. about one-third, alllofthefrace mate will be -precipitated admixture witli someofthe dextro tartrate, The precipitation oi the"? In the' eventthat it: isdesired to'remove-the precipitated tartr-ate atter standing: for less than twenty+four hours; thena any" non-precipitated dextro tartrate willbe recovered with the mesotartrate; Further a longe'n'standing, LthanZ-three days has been found not to be advisabler'duete increased; precipitation ofi ther' mes'oetartrate'.

H it "is dsite'd hot: 'to--"eifeet precipitation oi the basic salts, a1 further dilution 'ofthe brine "may ben-i'adei'iand thereupon" crystallization oi the nieso tartrate -takesplace: However, thiswrys tallization is slow and-=reqnire's at l'easfla week? for- '7-(l% separation; 'adyantaga'of thisprocedur' resids the fact' -that"it'yields"calcium meso-tar ate very pure condition-'- thus arecrystallization unnecessarjd and the f-re'' acid solution obtained 1 from it crystal lizes='easily -and maybe car r'i'ed' throng-h to dry nes's without a syrupy residu'ea- Th'e' basic" salt is' approximately two-thirds ines'otalfii ate and'bne third other niaterial. 1 This other '"iiiflfifiil i-ne-rueessaecnene a cid lalctonhnd sonie clexti e'tai tari'a acid -whic l i esca ed th'e first precipitation. The-greater part, however;-' con sists of non cr ystall-ihe acids of unk'n'ovvri com-- position? Further; the basic "salt may be 'dec'om pos'd diiectl'y wi-tl i sulphuric acid) but the pres ence'of so large-an amount "of non-crystalline-mw te'rial hinders recovery of the-*meso-tartaric "acid by increasing the density"of- *-the syrup whichoc--'-' casions slow crystallization.- Moreover; neutral izatfon'of thereaction mass containing the basic salt maybeeffectedwith aqueous ammonia; and wh'e'riiso conductedthere is "a lesser local f'orma ti6ri of"th"e' basic salt.

If'it is "uesi'r'e'mto recover a" further amount of calcium meso-tartriate from the filtrate fol-l lowing .separationof the-basic salt, this' may be brought about by adding calcium hydroxide to the filtrate-whereby 1 a furtherprecipitation as basic salts takes place.- In order to determinethe amount-oi?- hydrochloric acid' which shoui'dv be add'e de to; the? alkali-tie? brine? i to restore the pH value} the change-f 'methyI' rGd fromfiyellotw'tfi just red has been ieund to be-sufiicientmac= curate-L Moreover, a fractional precipitation fromthe oi iginat solutionl'ifiayvbe eficte'd byJadiiihg-ugnaduatedh amounts oi water thereto whicheoceasinns separatiom'of calcium-'macemata dUatGQthesxt-Eady hydrolysis of the calcium racemate-calci'um chloride complex, and thereby a, separation of the rac'emic acid from the dextro tartaric acid-. is brought about;

It 1 hfaslmbeeln: zf unduthaf; a e 12391911.; andel; cgmple fie i recovery of calcium mesa-tartrate may be accomplies-lied 'by':eXllliacfilng"fih" basi salt itate with a brine of 'about"39' 'B'. concentration. Inasmuch as the dextro tartaric acid has been removed, thequantity Gf bliihtliBQllitEd fontreat ment of the basic salt is considerably reduced. This procedure may be canried out by: reducing}: the reaction" mass" containing" the be saltsformed by treatment with calcium hydroxid to a relatively thick paste and adding, thereto about Sew-gallons of" 39 Br calcium chioride btinee The mixture is then brought to a pf-lffvalue of about 551 through the --introduction of 'about 50 gallons ofconcentrated hydrochloriw -aci-d-.- This is. followed 'byheatingwnearly, to the. boiling-point forltwenty minutes Tandlthen cooling; eactiommiiiture so obtained is fiiteremi r esse amt-washedi with" abouffid'gallons ofla 33! 'Ef br ne... The filter: cake so obtaineefis,"materiality dis-integratc'l'x byls'tirringa with 300 ganonsror 2:611:1 Water, filtered agam',. and 'WIasli'e dltithl Walt'l. Wltlfi ai-yild.0ff abbutil5'0' pounds. This filtrat'isfriow dilutdWO-about 1,500'gal1bn's; allbwdltosfanlii' for a period from. twelveto; sixteenlhburs dili ma hi h precipitationx occurs, land;-.i' he. precise itatexre (medias filtering-and wastiew thus obtained a further quantit bf'iiresowartra 3' in ant-amount of about pounds,- The fine filtrate? maybe treated? for reuse throilhathe addition of hydrochloric "acidf'to give -thejioriiii'al pHT-value; andvth'enl evaporated to i the initialvol ume;

the-foregoing presentation at mixture of about 70% calcium dextro-tartrate II-i and about 30 Viz-calcium meso=tartrater 3ii-lzQz-hasrbeen utilized foni illns'tnatiyerpurposesz Thefimeth'od, however, will vary in details 'in the etler'iiil that meshes-meme? ratios are separatedc it was found that over a-range ee zs t 35%0 I meso'tartrateinthe miXtur ahigfilysatfifictoryseparati'oniseficte'd. Mixtureshaviiiglss tfiaii 25% calcium meso-tartrate show'precipitati'on of pure calcium dextro tartrate=calciuirf chloride dilllbl'cbmpoflndfwhifi increases lifaill'dufit'wlth dcreasingumeso content; lviixturesl. containing more-thaw 35 calciummesortartrat precipitate thes: cor respond-lng.- pure mesocompounds amounts tincreasingetonearly quantitative when the dextro content reaches zeroa Consequently l the" changerequired -im the -separationi'pizocessstof adapt: it" to: any ratioof-mesm and centre;- is: a filtration: operation before-fi 'diluting the brine; The doublricompound separatingtwill beeitlien all dextro or all 'nieso deperi' rig on tl ie ratio of'thetwopresent. Becausebf' tlie'mome i tary soiubiiityof these double compounds in water; the. filter cake'shouldbewasliedwitlfun dilutdhiine rather than water. Ashortliki tionofT thefilter cake with-Iwater renew-meme washing ..r.ecovers-the normal .calium. salt.

Recovery: from: =mi-Xtlil1eS--0f0a1lummeEfi.i.-alid dextrct tart-rates? is illustrated .in-

the?" following tablet." It-ig'rtobernoticedcthat the process Ht-Him as eflioient in recovering the miiioir' contentment as' zthe majoi' onei whethenthistbenreso enema Distribution of normal calcium salt in mixtures of calcium meso tartrate (H120 and calcium clemtro tartrate 4H2O with 750 cc. 38% calcium chloride solution per 100 grams of calcium salt [Percent composition of mixtures] Calcium Meso 100 90 70 50 so 10 Calcium Dextro-.- 0 30 60 70 90 100 As calcium meso double 98.0 76.0 55. 4 25.4 none none none From the undiluted brine as double calcium chloride compound by compound.

heating for min., filtering, and lixiviation with an excess 0 water. As calcium dextro none none none none none 50.0 70.8

double compound.

From dilution of the filtered brine with 750 cc. H20 A? normal calcium dex- 0. 6 2. 4 23. 0 43. 6 65. 6 S5. 2 25. 2

From dilution further with a second 750 cc. H20 As normal calcium meso. none 14. 6 12. 4 21. 2 24. 6 2.6 1. 2

Recovered Total 98. 6 93. 0 90. 8 90. 2 90. 2 87. 8 97. 2

Material remaining dissolv l. 4 7. 0 9. 2 9. 8 9. 8 12.2 2. 8

Percent recovered of Calcium Meso 96. 9 93. 2 82.0 26. 0 76. 8 87. 2 93. 7 94. 7 96. 0

Moreover, a series of experiments in which mixtures of salts of hydroxy organic acids were treated with the concentrated salt solution by recycling the solution demonstrates that efficient separation could be made in this manner. No additions were made to the concentrated solution or brine, it being merely evaporated and made up to volume after each recovery. The procedure in outline was:

a. 100 gms. of mixed salt were treated with 750 cc. of calcium chloride solution of about 39 B. with heating and stirring to complete the solution.

for two hours, cooling with circulating tap water.

0. Filtered and washed with water, the washings being retained for diluting the next cycle at step b.

filtrate.

e. Heated with stirring, minutes.

1. Cooled with stirring, 30 minutes.

9. Filtered and washed.

it. Filtrate adjusted to pH 5.1 (methyl red) with 20 B. technical I-ICl.

q i.-Filtrateevaporated en vacuo to 750 00., agitating with an air stream admitted through a course capillary.

7'. Repeat a, etc.

Furthermore, the method may be applied for the separation of hydroxy from non-hydroxy acids, e. g. of oxalic acid from the tartaric acids or from lactic acid inasmuch as the calcium salts thereof as calcium oxalate are not dissolved in the concentrated salt solution especially the calcium chloride brine,

The procedure hereinab-ove described is at-- tended by many advantages among which may be mentioned that it is economical because the separations are practically quantitative with the dextro and meso-tartaric acids and the saccharic acids being obtained as their substantially pure calcium salts. Further the precipitates are easily filtered and readily washed; the calcium chloride brine may be evaporated to the desired Baum after the precipitates have been separated therefrom and the brine accordingly reused; any calcium salt remaining in the calcium chloride brine is returned to the cycle of operations; and hence any loss in the desired acids would be limited merely to mechanical losses; the salts obtained are white and yield colorless solutions, and :any acid which is not fully separated, such as a small amount of meso-tartaric acid in the dextro portion, is recovered in the 5 crystallization of the free acids as a residue which may be returned to the process.

Since certain changes may be made in carrying out the above method without departin from the scope of the invention, it is intended that all 30 matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein deb. Added 750 cc. water and continued stirring scribed, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described my invention what I claim 40 as new and desire to secure by Letters Patent is: d. Added 10 gms. technical slaked lime to the i 1. A method for the separation of hydroxy organic acids which comprises quantitatively separating such acids by dissolving a mixture of salts of hydroxy organic acids in a concentrated solution of a highly soluble salt of a metal forming a highly soluble chloride and an insoluble salt of the organic acid to form a metal salt of such organic acid which is soluble in a concentrated solution but insoluble in a dilute solution of said highly soluble metal salt, diluting the solution so produced with ensuing precipitation of said metal salt, removing precipitated salt, converting the unprecipitated organic acids into insoluble basic salts by reaction with an alkaline hydroxide,

, 5 removing basic salts so produced, and converting o0 separating such acids by dissolving a mixture of hydroxy organic acids in the form of calcium salts in a concentrated calcium chloride solution having a pH value of about 5.1 to form a salt of such organic acid which is insoluble in a con- 5 centrated solution but insoluble in a dilute solution of calcium chloride, diluting the solution so produced with ensuing precipitation of such salt, removing precipitated salt, converting the unprecipitated organic acid into insoluble basic 7c salts by reaction with calcium hydroxide at a temperature of about C., removing basic salts so produced, and converting them into the corresponding acids by treatment with an inorganic acid.

.75 3. A method for the separation of hydroxy organic acids which comprises quantitatively separating such acids by dissolvin a mixture of tartrates in a concentrated solution of a highly soluble salt of a metal forming a highly soluble chloride and an insoluble tartrate, to form dextro and racemic tartrates which are soluble in a concentrated solution but insoluble in a dilute solution of said highly soluble metal salt, diluting the solution so produced with ensuing precipitation of such dextro and racemic tartrates, removing precipitated salts, converting unprecipitated meso-tartaric acid into its insoluble basic salt by reaction with an alkaline hydroxide, removing basic salt so produced, and converting it into meso-tartaric acid by treatment with a stronger acid.

4. A method for the separation of hydroxy organic acids which comprises quantitatively separating such acids by dissolvin a mixture of calcium tartrates under the influence of heat and stirring in a calcium chloride brine of about 34 to about 47 B., to fonn calcium dextro and racemic tartrates which are soluble in a concentrated solution but insoluble in a dilute solution of calcium chloride, diluting the solution thus formed with substantially an equal volume of water with ensuing separation of normal calcium dextro and racemic tartrates by precipitation, removing precipitated dextro and racemic tartrates, converting unprecipitated meso-tar taric acid into its insoluble basic salt by reaction with calcium hydroxide, removing basic mesotartrate so produced and converting it into mesotartaric acid by treatment with an inorganic acid.

5. A method for the separation of hydroxy organic acids which comprises quantitatively separating such acids by dissolving a mixture of calcium tartrates in a calcium chloride brine of about 34 to about 47 B., to form dextro and racemic tartrates which are soluble in a concen trated solution but insoluble in a dilute solution of calcium chloride, diluting the solution so produced with ensuing separation of normal calcium dextro and racemic tartrates by precipitation, removin the precipitated tartrates, converting unprecipitated meso-tartaric acid into its insoluble basic salt by reaction with calcium hydroxide, reducing the reaction mixture to a paste, treating the paste so obtained with calcium chloride brine of about 39 B., adding hydrochloric acid thereto to give a pH value of about 5.1, heating, and then cooling whereupon a mesotartrate separates as a precipitate.

6. In a method for the separation of hydroxy organic acids the improvement which comprises dissolving a mixture of salts of hydroxy organic acids in a concentrated solution of a highly soluble salt of a metal which forms a highly soluble chloride and an insoluble salt of the organic acid to form a metal salt of such organic acid which is soluble in a concentrated solution but insoluble in a dilute solution of said highly soluble metal salt, and diluting the solution so obtained with ensuing separation of such metal salt by precipitation.

7. In a method for the separation of hydroxy organic acids the improvement which comprises a quantitative separation thereof including the steps of dissolving a mixture of salts of hydroxy organic acids in a. solution of a highly soluble salt 10 of a metal which forms a highly soluble chloride and an insoluble salt of the organic acid having a concentration from about 34 to about 47 B. and a pH value of about 5.1.

3. In a method for the separation of hydroxy organic acids the improvement which comprises a quantitative separation thereof including the step of dissolvin a mixture of calcium tartrates in a calcium chloride solution having a concentration from about 34 to 47 B. and a pH value of about 5.1.

9. In a method for the separation of tartaric acids the improvement which comprises a quantitative separation thereof including the steps of dissolving a mixture of calcium tartrates in a concentrated calcium chloride solution to form dextro and racemic tartrates which are soluble in a concentrated solution but insoluble in a dilute solution of calcium chloride, and diluting the solution so obtained with ensuing separation of calcium dextro tartrate by precipitation.

10. In a method for the separation of hydroxy organic acids the improvement which comprises a quantitative separation thereof including the step of dissolving a mixture of hydroxy organic acids in the form of their calcium salts in a solution of calcium chloride having a concentration from about 34 to about 47 B.

11. As a composition of matter, a metal salt of a hydroxy organic acid which is soluble in a concentrated solution but insoluble in a dilute solution of a highly soluble salt of a metal which forms a highly soluble chloride and an insoluble salt of the organic acid.

12. As a composition of matter, a calcium salt of a tartaric acid which is soluble in a solution of calcium chloride having a concentration from about 34 to about 47 B. but insoluble in a dilute solution thereof.

13. A method for the separation of hydroxy organic acids which comprises quantitatively separating tartaric acids by dissolving a mixture of calcium tartrates in a calcium chloride brine of about 34 to about 47 B. with formation of tartrates which are soluble in a concentrated solution but insoluble in a dilute solution of calcium chloride, diluting the solution thus formed with ensuing separation of calcium dextro and racemic tartrates by precipitation, removing the precipitated tartrates, and further diluting the solution with ensuing separation of calcium meso-tartrate by precipitation and removing the meso-tartrate so produced.

WILLIAM E. BARCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,425,605 Odell Aug. 15, 1922 1,870,472 Stokes et a1. Aug. 9, 1932 2,382,288 Braun et al Aug. 14, 1945 OTHER REFERENCES Paul: Zeitschrift fiir Electrochemie, Bd. 21, pp. 548-549 (1915). 

